If you’re like most people, you probably turn on your car’s heater when it starts to get cold outside. But did you know that you can also turn on the heater in your car using the controls on the dashboard? Here’s how: To turn on the heater in a car, first make sure that the car is in “Park.” Then press and hold down the “Heater” button until the light next to it turns green. To turn off the heater, press and hold down the “Heater” button until the light next to it turns red. ..